In applying a low frequency to a patient in the case of conventional low frequency therapeutic instruments, if the low frequency of a high voltage is given from the beginning, it will not only shock and discomfort the human body but will be also sometimes even detrimental, and general usage of these therapeutic instruments has been such that the user gradually elevates the output of low frequency pulses with the volume or the like of an output adjusting circuit to use the instrument at a proper voltage. This is also the same in the case that the therapy of one portion of the human body ends and then a conductor is contacted with another body portion, thus the voltage must be elevated to a proper level at each time through a manual adjustment, and there has been involved a problem that the handling is complicate.
Further, in the conventional low frequency therapeutic instruments, the output wave form of the low frequency pulses is generally a rectangular wave form which is not particularly shaped in the wave form, and there has been a problem that a pain will be given to the patient in the rising part of the wave form.